Land-based vehicles are able to travel through a body of water to a finite depth, which may be referred to as a maximum wading depth. The maximum wading depth of a vehicle is very much dependent upon the design of the vehicle.
For example, it is common for off-road type vehicles to be configured such that they can be driven through a body of water of significant depth, for example 500 mm, 700 mm or more. Driving through a body of water having a significant depth is often referred to as wading. Driver caution and judgement is required when a vehicle is wading or is about to enter into a wading scenario. This is because a vehicle driver typically does not know the depth of water that the vehicle is about to enter or the nature of the terrain below the water surface. It is recommended that a survey of the terrain is taken by wading through water on foot, but factors such as the variability of the terrain; low visibility conditions; inconvenience to the driver; and driver impatience may result in a driver attempting to traverse water without knowledge of the water depth and therefore without being able to take appropriate precautions. Furthermore, the nature of the terrain may be variable and a full picture of the terrain and changing water depth may not be gathered very effectively by a vehicle driver wading through water on foot.
In other vehicle examples, such as sports models, a vehicle may not be specifically designed for wading and the position of water sensitive components and/or inlets, such as the air intake, may be relatively low. The maximum wading depth of such a vehicle may be only about 200 mm or 250 mm. For such vehicles there is a risk that the vehicle engine and electronics may be damaged even if the vehicle is driven through a body of water of relatively low depth, for example 200 mm or even less (due to displacement of the water as the vehicle travels through it).
It is therefore desirable to obtain accurate information relating to the environment a vehicle is currently in, or is about to enter. It is of particular advantage to ascertain, in advance of a vehicle being disposed in a body of water, an estimation of the depth of that body of water. Such information may be: conveyed to the driver to improve driver control during vehicle wading; used to manually or automatically activate one or more vehicle control mechanisms which may be used to prepare and/or protect the vehicle as it goes into a wading situation; and/or used to alert the driver to a potentially vehicle damaging situation, to guide the driver to cease the progression of the vehicle towards the water or further into the water.
Embodiments of the present invention seek to provide an improvement in the field of liquid (particularly, water) depth estimation systems that has particular application for vehicles and, more specifically but not exclusively, to land-based automotive vehicles. Embodiments of the invention may be utilised in applications other than for vehicles; for example, it is envisaged that embodiments of the invention may have application in buildings, for example domestic houses, where the automatic detection of water at a certain level may be useful. Such a system may be adapted, for example, to effect automatic deployment of flood defence systems. The invention may be utilised in un-manned vehicles.